To produce the electromagnetic (E&M) precursors of an earthquake, the existence of electric field due to stress-induced charges on the ground surface or in shallow depths of upper crust inside the fault zone is a basic condition. Here, we consider the piezoelectric effect or the elastic-electric coupling as a major mechanism on generating such an electric field. A one-dimensional model based on the elastic mechanics and electromagnetic Maxwell equations is built up to formulate the relationship between electric field and slip as well as stress on a fault before an earthquake. From the model, we may estimate the low-bound values of stress and slip to yield the critical electric field, E_c, for generation of electromagnetic signals. The normal and shear stresses on the fault planes for three faulting types are constructed. The normal stress is stronger than the shear stress to result in piezoelectricity. The depth ranges for yielding an average normal stress being able to generate E_c are similar for thrust and strike-slip faults and deep for normal faults. The possibility of generating E_c is almost the same for thrust and strike-slip faults and low for normal faults. The pre-earthquake slip could be related to nucleation phases or microfractures. The possible occurrence time of E&M signals may be several ten minutes to few hours before impending earthquakes. The major factor in yielding a piezoelectric field to generate the TEC anomalies before an earthquake is the existence of fault gouges composed mainly of clays. A thick gouge layer with low electric resistivity and a piezoelectric coupling coefficient ≥ 0.67 × 10⁻¹² coul/nt is an important condition for yielding piezoelectricity.

中文翻译：

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压电作为地震前电磁前驱物生成的机制

为了产生地震的电磁（E＆M）先兆，断层区域内地面或上地壳浅层深度中的应力感应电荷所引起的电场的存在是基本条件。在此，我们将压电效应或弹性电耦合作为产生这种电场的主要机制。建立了基于弹性力学和电磁麦克斯韦方程组的一维模型，以计算电场与滑动以及地震前断层上的应力之间的关系。从模型中，我们可以估计应力和滑移的低界值，以产生临界电场E _c，用于产生电磁信号。构造了三种断层类型的断层平面上的正应力和剪应力。正应力比剪切应力强，从而导致压电性。对于推力和走滑断层，产生能够产生E _c的平均法向应力的深度范围相似，而对于法向断层，深度范围相似。产生E _c的可能性对于推力和走滑断层几乎是相同的，而对于正常断层则几乎为低。地震前的滑移可能与成核阶段或微裂缝有关。E＆M信号可能发生的时间可能在即将发生地震前的几十分钟到几小时。地震前产生压电场以产生TEC异常的主要因素是主要由黏土组成的断层泥的存在。具有低电阻率和≥0.67 ×  10 ^-12 coul / nt的压电耦合系数的厚的凿层 是产生压电性的重要条件。